1. Field of the Invention
The present invention relates to liquid phase olefin polymerization, to the preparation of polyolefin products and to apparatus useful in the preparation of polyolefin products. In particular the present invention relates to apparatuses and equipment for the preparation of a variety of polyolefin products using a liquid phase polymerization process and to the methodology used in the operation of such apparatuses and equipment. More particularly, the present invention relates to apparatus and methodology which enhances the operation and control of polyolefin reactors.
2. Background of the Invention
Presently pending U.S. patent application Ser. No. 09/515,790 filed on Feb. 29, 2000 and entitled “Process For Producing High Vinylidene Polyisobutylene” (hereinafter the '790 application) relates to liquid phase polymerization processes for preparing low molecular weight, highly reactive polyisobutylene. In accordance with the disclosure of the '790 application, a catalyst composition, which desirably may comprise a complex of BF3 and methanol, and a feedstock containing isobutylene, are each introduced into a reaction zone where the same are intimately admixed with residual reaction mixture so as to present an intimately intermixed reaction admixture in the reaction zone. The intimately intermixed reaction admixture is maintained in its intimately intermixed condition and at a relatively constant temperature of at least about 0° C. while the same is in the reaction zone, whereby isobutylene therein is polymerized to form polyisobutylene (PIB) having a high degree of terminal unsaturation. A crude product stream comprising residual catalyst composition, unreacted isobutylene and polyisobutylene is then withdrawn from the reaction zone. The introduction of feedstock into and the withdrawal of product stream from the reaction zone are each controlled such that the residence time of the isobutylene undergoing polymerization in the reaction zone is no greater than about 4 minutes, whereby the product stream contains a highly reactive polyisobutylene product. Preferably, the reaction zone may be the tube side of a shell-and-tube exchanger in which a coolant is circulated on the shell side. A recirculation loop may desirably be employed to circulate the reaction admixture through the tube side reaction zone at a linear velocity sufficient to establish and maintain an intimately intermixed condition in the admixture and remove heat generated by the exothermic polymerization reaction.
U.S. Pat. No. 6,525,149 issued on Feb. 25, 2003 and entitled “Process For Preparing Polyolefin Products” (hereinafter the '149 patent) relates to a novel liquid phase polymerization process for preparing a polyolefin product having preselected properties. The process of the '149 patent includes the steps of providing a liquid feedstock which contains an olefinic component and a catalyst composition which may comprise a stable complex of BF3 and a complexing agent. The feedstock may comprise any one or more of a number of olefins, including branched olefins such as isobutylene, C3-C15 linear alpha olefins and C4-C15 reactive non-alpha olefins. The feedstock and the catalyst composition may desirably be introduced into a residual reaction mixture recirculating in a loop reactor reaction zone provided on the tube side of a shell and tube heat exchanger at a recirculation rate sufficient to cause intimate intermixing of the residual reaction mixture, the added feedstock and the catalyst composition. The heat of the polymerization reaction is removed from the recirculating intimately intermixed reaction admixture at a rate calculated to provide a substantially constant reaction temperature therein while the same is recirculating in the reaction zone. The conditions in the reactor are appropriate for causing olefinic components introduced in the feedstock to undergo polymerization to form the desired polyolefin product in the presence of the catalyst composition. A crude product stream containing the desired polyolefin product, unreacted olefins and residual catalyst composition is withdrawn from the reaction zone. The introduction of the feedstock into the reaction zone and the withdrawal of the product stream from the reaction zone are controlled such that the residence time of the olefinic components undergoing polymerization in the reaction zone is appropriate for production of the desired polyolefin product.
U.S. Patent publication 2003-0040587 A1 published on Feb. 27, 2003 and entitled “Mid-Range Vinylidene Content Polyisobutylene Polymer Product And Process For Producing The Same” (hereinafter the '587 publication) describes a mid-range vinylidene content PIB polymer product and a process for making the same. In accordance with the disclosure of the '587 publication, at least about 90% of the PIB molecules present in the product comprise alpha or beta position isomers. The alpha (vinylidene) isomer content of the product may range from 20% to 70% thereof, and the content of tetra-substituted internal double bonds is very low, preferably less than about 5% and ideally less than about 1-2%. The mid-range vinylidene content PIB polymer products are desirably prepared by a liquid phase polymerization process conducted in a loop reactor similar to the reactors described in the '790 application and the '587 patent at a temperature which desirably may be about 60° F. or higher using a BF3/methanol catalyst complex and a contact time of no more than about 4 minutes.
The '790 application, the '587 publication and the '149 patent are each assigned to the assignee of the present application, and the entireties of the respective disclosures thereof are specifically incorporated herein by this reference thereto.
In conducting the reactions described above, highly specialized equipment may often be employed to enhance the operation and control of the polymerization reactors. In each case, for example, the crude product leaving the reactor may be contaminated with residual catalyst which desirably should be quickly quenched or killed to avoid further polymerization of monomers and low molecular weight oligomers without appropriate cooling and/or isomerization resulting from shifting of the position of the remaining double bond. The catalyst composition may be subjected to contamination by residual materials recirculating with the reaction admixture during the conduct of the polymerization reaction. Moreover, as in any industrial activity, methodology and/or equipment for enhancing capacity and throughput are sought continually.